1. Field of the Invention
The present invention relates to an apparatus for detecting the amount of developer that detects such amount in the developer containers of a developing device used for an image formation apparatus of a copying machine or a laser beam printer that adopts the electrophotographing method. The invention also relates to a process cartridge using this developer amount detection apparatus.
In this respect, the process cartridge comprises at least one of developing means serving as processing means, electrostatic charging means and cleaning means, and an electrophotographic photosensitive body. These are arranged integrally in the form of a cartridge, and then, this cartridge is made detachably mountable on the main body of the image formation apparatus.
2. Related Background Art
Conventionally, it is required for the image formation apparatus: such as a copying machine, to replace the photosensitive drum that serves as the image carrier as well as the developing device in order to supply the toner that serve as developer; to clean the discharge wires of the electrostatic charger; to exchange the cleaning containers in which the waste toner is accumulated; and to adjust or replace devices around the photosensitive drum when the image formation apparatus is used for a long time.
However, special skills and knowledge are needed for carrying out such maintenance as described above, making it rather difficult for a general user to execute it.
Therefore, it has been proposed and put into practice that the photosensitive drum and the developing device, the electrostatic charger, and the processing device such as the cleaning equipment, are integrally assembled in a cartridge container, and that such cartridge is detachably mounted on the main body of an image formation apparatus as a process cartridge. In this manner, when there is a need for the maintenance of the processing equipment, the entire body of the process cartridge is replaced to make it easier to implement the intended maintenance.
Now, however, the process cartridge should be replaced with a new cartridge when the toner retained in it in advance is completely consumed. Here, therefore, the arrangement is made so that the user is able to determine the remaining toner at all times and take precaution against any sudden shortage of toner.
In this respect, a toner amount detection apparatus is arranged in the interior of a toner container to detect the amount of toner in the toner container. FIG. 5 to FIG. 7 illustrate one example of the toner amount detection apparatus.
In other words, FIG. 5 is a cross-sectional view which shows the process cartridge provided with such toner amount detection apparatus. FIG. 6 is a view which shows the main part of the toner amount detection apparatus. FIG. 7 is a cross-sectional view taken along line 7--7 in FIG. 6. The toner amount detection apparatus adapts the method to enable the float 11, which is a member for detecting the position for the amount of developer, which is supported by a rotational float arm 12, in order to follow the shifting upper surface position of the toner, hence detecting the toner remainders continuously.
Now, as a method for holding the toner surface by use of the float 11, the float arm 12 is installed on the rotational float shaft 13 in the interior of the toner container 3 in accordance with this example, and a recovery lever 100 is fixed to the end portion of the float shaft 13, which is extruded outside the toner container 3. In this way, it is arranged to keep the rotated positions (rotational angles) of both of them unchanged.
Then, when the user pulls up the recovery lever 100 before the process cartridge is installed on the main body of the image formation apparatus, it is made possible for the float 11 to hold the toner surface again even if the float 11 is buried in the toner before use. When the cartridge is in use, the float 11 rotates to follow the toner surface in the direction indicated by an arrow Ya as the toner surface descends from (A) to (B).
However, there are the problems discussed below as to the toner amount detection apparatus that has been discussed above.
In other words, as the toner surface, which is held by the float 11, approaches the agitation member 4, the toner surface begins to be influenced by the agitation thereof. On the surface, undulation takes place to make it softer. Thus, the float 11 sinks into the toner eventually. This makes it impossible to detect the toner remainders exactly in the toner container 3.
Also, in order to make the detection possible even when the toner remainders become smaller still, it is conceivable to arrange the float 11 and the agitation member 4 so that their paths may cross each other by lowering the position of the float shaft 13 as shown in FIG. 8. However, if the rotational direction of the agitation member 4 is as indicated by an arrow Yb, there is the possibility that the float 11 advances excessively in the direction indicated by an arrow Ya when the agitation member 4 is in contact with the float 11. As a result, it becomes impossible to detect exactly the toner remainders in the toner container 3.
Further, as described above, if the position of the float shaft 13 is lowered to allow the paths of the float 11 and the agitation member 4 to intersect each other, the agitation member 4 tends to push away the float 11 in the direction indicated by the arrow Ya when the float abuts upon the agitation member 4 after rotating in the direction indicated by an arrow Yc at the time that the float 11 comes to a stop by abutting upon the toner container 3 as shown in FIG. 9 (because the acting point of the force exerted by the agitation member 4 on the float 11 is in the right side of the center in FIG. 9). However, since the toner container 3 does not allow the float 11 to escape anyway, the agitation member 4 can no longer operate normally once it abuts upon the float 11.